Zotero is a computer application that allows you to easily keep track of your sources!
Click on this link to go to the Zotero webpage: https://www.zotero.org/
To work properly, Zotero must be added as an extension to your web browser AND the downloaded application must be open.
Click on the Zotero Extension (shown in the image) and Zotero will save the web page you are currently on-- as well as whatever information it can find about the source-- to the folder of your choosing! It's recommended that you make a new folder in Zotero for every new paper you write.